"/ch/ is pronounced very lightly, like its Vietnamese correspondent." Maybe /ȶ/ rather than /tɕ/?
/ɬ wˀ jˀ/ only occur in word-final position. Maier also includes "/yh/ - a voiceless alveopalatal fricative", but this description is the same as for /s/, which Maier says can't occur word-finally. (Maybe /ɬ/ could be unified with /ɾ/?)
/e̝ e ɛ/ could alternatively be described as /e ɛ æ/, following the textual descriptions.